1. Field of the Invention
The present invention relates to a method of removing a photosensitive belt of a printing apparatus from rollers of a belt unit for repair or replacement.
2. Description of the Related Art
In general, as shown in FIGS. 1 and 2, a printing apparatus such as a printer or copier is comprised of a frame 10 having a belt passage 11, a belt unit 20, a developing device 30, a transfer roller 41 and a fixing roller 42. The belt unit 20 includes rollers 21, 22 and 23, and a photosensitive belt 25 circulating around the rollers 21, 22 and 23.
During printing, a toner image is formed on one surface of the circulating photosensitive belt 25 by the developing device 30, the toner image is transferred and fixed on a sheet of paper 1 passing through between the transfer roller 41 and the fixing roller 42, and the image is printed on the sheet of paper 1. On the other hand, when so-called lateral slip occurs, i.e., the photosensitive belt 25 looped around the rollers 21, 22 and 23 circulates in a slightly oblique direction with respect to the rollers 21, 22 and 23 and does not circulate in a perpendicular direction with respect to the rollers 21, 22 and 23, the photosensitive belt 25 moves in a direction which increases the tension of the photosensitive belt 25 along a lengthwise direction of the rollers 21, 22 and 23, and consequently the quality of print is lowered. Therefore, in general, a printer is provided with a sensor (not shown) for detecting lateral slip of the photosensitive belt 25, and a steering device which corrects the lateral slip by slanting at least one of the rollers 21, 22 and 23 with respect to the others based on the signal from the sensor. Such a steering device is known in the field of the art, those of various configurations are presently used, and an example of those is disclosed in U.S. Pat. No. 5,479,241.
In such a printer, when the performance of the photosensitive belt 25 looped around the rollers 21, 22 and 23 deteriorates, the photosensitive belt 25 must be removed from the rollers 21, 22 and 23 through the belt passage 11 of the frame 10 so that it can be replaced with a new one.
In removing the photosensitive belt 25 from the rollers 21, 22 and 23, any one roller 21 is moved toward the other rollers 22 and 23 as shown by the imaginary line in FIG. 1 so that the tension applied to the photosensitive belt 25 for smooth circulation of the photosensitive belt 25 can be removed, and the photosensitive belt 25 can be freed from the rollers 21, 22 and 23. After the roller 21 is moved to the position shown in phantom in FIG. I and the tension of the photosensitive belt 25 is relieved, the photosensitive belt 25 looped around the rollers 21, 22 and 23 is removed from the rollers 21, 22 and 23 through the belt passage 11 of the frame 10. When a new photosensitive belt is looped around the rollers 21, 22 and 23, the roller 21 is moved back to the position shown by the solid line in FIG. 1, and applies tension to the new photosensitive belt 25.
However, in the above-described method, since the space between the belt passage 11 and the belt unit 20 is very narrow, it is difficult for a worker to directly remove the photosensitive belt 25 by inserting a hand through the belt passage 11, and, in addition, since the rollers 21, 22 and 23 are heated to a high temperature, the worker may suffer a burn while removing the photosensitive belt 25 from the rollers 21, 22 and 23.
In view of the above, a belt receiving cartridge is used to insert the belt into the belt passage by first receiving the belt in the belt receiving cartridge, and then to cause the belt to be removed through the belt passage by taking out the belt receiving cartridge, or to remove the photosensitive belt from the rollers by using a separate removing means. However, in the method using the belt receiving cartridge or the separate removing means as described above, there is a problem in that the belt removal is complicated. In addition, there is a problem in that when the belt receiving cartridge or the separate removing means is inserted into or removed from the frame through the belt passage, the belt receiving cartridge or the separate removing means may touch and damage the rollers.
To solve the above problems, it is an objective of the present invention to provide a method of removing a photosensitive belt of a printing apparatus from rollers, which is improved so that the photosensitive belt can be easily removed from the rollers without causing damage to the rollers even when a separate removing means is not used.
Accordingly, to achieve the above objective, there is provided a method of removing a photosensitive belt of a printing apparatus by removing the photosensitive belt, which is looped and circulating around a plurality of rollers in a tensioned state in the printing apparatus, through a belt passage provided at the frame of a printing apparatus including the steps of: circulating the photosensitive belt with at least one roller slanted with respect to the other rollers so that the photosensitive belt moves laterally in a lengthwise direction of the rollers and a portion part of the photosensitive belt is projected through the belt passage; and removing the photosensitive belt completely from the rollers by pulling the portion of the photosensitive belt which is projected through the belt passage.